A setting, or campaign setting, is the time and place in which a campaign or other role-playing game is supposed to be set. To the extent that setting information is understood and agreed by the a group's players, it is part of that group's system because players (and, perhaps more importantly, the GM) will be influenced by their understanding and expectations of the setting to make decisions that impact the events in the fiction.
The amount of established information about a setting will vary considerably between games. Some settings take place on something like the real world and include only information that explains how the setting differs from reality; others take place on imaginary worlds, and may need to describe original places, creatures, cultures and metaphysical laws (for example). Some settings will intentionally include only a small amount of information, allowing more to be established during play.
Groups may either create their own campaign settings (called homebrew settings) or use a (fully or partially) pre-generated setting. Most published games include at least one sort of pre-generated setting, which may be from the following types:
- integrated setting, when system mechanics are so connected to the setting that no other setting can be used without extensive hacking;
- default setting, when one specific setting is provided by the game rules, but the game could support others;
- alternate setting, a setting that can be used instead of a game's default setting;
- implicit setting, when no setting information is provided explicitly but some facts about the setting can be determined from the game's rules;
- example setting, generally found in generic role-playing games (in which groups are expected to use their own settings) by providing an example of a setting that is used to explain the rules but never intended to be used in an actual game.
Some settings also exist independently of any games, for example settings from established franchises and intellectual property (e.g. Star Wars or the DC Universe). These may be used in officially licensed games as default, alternate or integrated settings, or homebrewed by players into other game systems. Sometime, setting books are published for RPG consumers that include settings that can be used in multiple game systems.